Dryland state transitions alter trophic interactions in a predator-prey system

Area of Science:

• Ecology
• Environmental Science
• Wildlife Biology

Background:

• Environmental change impacts trophic interactions and food web dynamics, affecting ecosystem stability.
• Mechanisms linking environmental change to top-down and bottom-up processes are not well understood.
• Shrub encroachment is a significant environmental change in dryland ecosystems.

Purpose of the Study:

• To investigate how shrub encroachment affects trophic interactions in a dryland predator-prey system.
• To evaluate hypotheses concerning bottom-up, top-down, and intraguild interactions under environmental change.
• To understand the role of perceived predation risk in shaping these interactions.

Main Methods:

• Utilized 7 years of camera trap data from the Chihuahuan Desert, New Mexico.
• Examined a predator-prey system: coyotes, kit foxes, jackrabbits, and cottontails.
• Employed structural equation modeling across grassland-to-shrubland gradients with variable precipitation.

Main Results:

• Lagomorphs responded to precipitation pulses in shrub-covered areas, suggesting altered bottom-up effects.
• Shrub cover influenced perceived predation risk, reducing it for lagomorphs in shrub-dominated habitats.
• Coyotes restricted kit fox space use, with this intraguild interaction influenced by shrub encroachment.

Conclusions:

• Environmental change, like shrub encroachment, alters trophic interactions beyond traditional top-down/bottom-up dynamics.
• Perceived predation risk is a key mechanism through which environmental change affects food webs.
• Findings have implications for understanding herbivory patterns and shrubland persistence in drylands.